It is known that an elevator motion control system may employ motor speed (or velocity) feedback control to achieve desired control of elevator car motion. In such a control system, the motor velocity control comprises a velocity outer loop having a proportional-plus-integral forward path control compensation and a velocity inner loop having proportional (gain) control. The inner velocity loop provides damping to the overall control system.
In order for the performance of the control to provide the desired response, travel time and/or ride quality performance, the inner loop is calibrated to match the characteristics of the elevator and motor being controlled. In particular, it is desirable to match the inner loop gain to the system inertia (J) and the motor torque constant (K.sub.T) parameters. However, in modernization or retrofit applications, where a new controller replaces an older controller in an existing elevator system, the inertia and/or torque constant parameters are not always accurately known at the time of installation of the controller. Alternatively, if the weight of the cab changes after drive installation, e.g., by adding or removing fixtures, mirrors, tile, etc., the system inertia changes and the motor/drive system may need to be re-calibrated.
One technique for determining such parameters is to dispatch a field engineer to the site who tunes the elevator controller using special test equipment, e.g., external signal generators and separate torque perturbations. Also, determination of the inertia parameter may be determined by the complex calculation of system weights from contract data which may or may not be accurate at a given job site. Further, in many instances, all the system masses are not accurately known, and thus accurate calculation of system weights is not feasible. However, such techniques are costly, time consuming and, in some cases, inaccurate. As a result, re-calibration of the system is costly and modernization or retrofit applications become unattractive for building owners.